rapid eye movement

Discovered in 1953, phases of sleep during which the eyes move rapidly (although the eyelids are closed). Also known as REM, these phases occur at regular intervals during sleep (there is a cycle which lasts about 90 minutes).

-Amount of REM-sleep positively correlates with IQ among children, that is: Intelligent children have more REM than usual.

-Selective REM-sleep deprivation has a similar effect to antidepressants such as Prozac on depression; a lasting positive effect that takes a few weeks to develop. And also, it seems that ALL medications that have an antidepressant effect causes some degree of selective REM sleep deprivation.

-In addition to the memory/consolidation hypothesis of REM sleep, there is the brain development hypothesis. REM sleep serves development of the brain. The hypothesis is supported by these facts:
--The period in our life that we spend most time in REM sleep is the same period in which our brain development is at its peak.
--The amount of REM sleep decreases throughout life from 70% of total sleep time as newborns, to 15% in late adulthood.
--New-borns of species that are born with well-developed brains (such as the guinea pig), spend proportionally less time in REM sleep than new-borns of species where the brain development is very active after birth (e.g. humans)